const Crypto = {};

(function(){

var base64map = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'


// Crypto utilities
var util = Crypto.util = {

	// Bit-wise rotate left
	rotl: function (n, b) {
		return (n << b) | (n >>> (32 - b))
	},

	// Bit-wise rotate right
	rotr: function (n, b) {
		return (n << (32 - b)) | (n >>> b)
	},

	// Swap big-endian to little-endian and vice versa
	endian: function (n) {

		// If number given, swap endian
		if (n.constructor == Number) {
			return util.rotl(n, 8) & 0x00FF00FF |
			       util.rotl(n, 24) & 0xFF00FF00
		}

		// Else, assume array and swap all items
		for (var i = 0; i < n.length; i++)
			n[i] = util.endian(n[i])
		return n

	},

	// Generate an array of any length of random bytes
	randomBytes: function (n) {
		for (var bytes = []; n > 0; n--)
			bytes.push(Math.floor(Math.random() * 256))
		return bytes
	},

	// Convert a string to a byte array
	stringToBytes: function (str) {
		var bytes = []
		for (var i = 0; i < str.length; i++)
			bytes.push(str.charCodeAt(i))
		return bytes
	},

	// Convert a byte array to a string
	bytesToString: function (bytes) {
		var str = []
		for (var i = 0; i < bytes.length; i++)
			str.push(String.fromCharCode(bytes[i]))
		return str.join('')
	},

	// Convert a string to big-endian 32-bit words
	stringToWords: function (str) {
		var words = []
		for (var c = 0, b = 0; c < str.length; c++, b += 8)
			words[b >>> 5] |= str.charCodeAt(c) << (24 - b % 32)
		return words
	},

	// Convert a byte array to big-endian 32-bits words
	bytesToWords: function (bytes) {
		var words = []
		for (var i = 0, b = 0; i < bytes.length; i++, b += 8)
			words[b >>> 5] |= bytes[i] << (24 - b % 32)
		return words
	},

	// Convert big-endian 32-bit words to a byte array
	wordsToBytes: function (words) {
		var bytes = []
		for (var b = 0; b < words.length * 32; b += 8)
			bytes.push((words[b >>> 5] >>> (24 - b % 32)) & 0xFF)
		return bytes
	},

	// Convert a byte array to a hex string
	bytesToHex: function (bytes) {
		var hex = []
		for (var i = 0; i < bytes.length; i++) {
			hex.push((bytes[i] >>> 4).toString(16))
			hex.push((bytes[i] & 0xF).toString(16))
		}
		return hex.join('')
	},

	// Convert a hex string to a byte array
	hexToBytes: function (hex) {
		var bytes = []
		for (var c = 0; c < hex.length; c += 2)
			bytes.push(parseInt(hex.substr(c, 2), 16))
		return bytes
	},

	// Convert a byte array to a base-64 string
	bytesToBase64: function (bytes) {

		// Use browser-native function if it exists
		if (typeof btoa === 'function') return btoa(util.bytesToString(bytes))

		var base64 = [],
		    overflow

		for (var i = 0; i < bytes.length; i++) {
			switch (i % 3) {
				case 0:
					base64.push(base64map.charAt(bytes[i] >>> 2))
					overflow = (bytes[i] & 0x3) << 4
					break
				case 1:
					base64.push(base64map.charAt(overflow | (bytes[i] >>> 4)))
					overflow = (bytes[i] & 0xF) << 2
					break
				case 2:
					base64.push(base64map.charAt(overflow | (bytes[i] >>> 6)))
					base64.push(base64map.charAt(bytes[i] & 0x3F))
					overflow = -1
			}
		}

		// Encode overflow bits, if there are any
		if (overflow != undefined && overflow != -1)
			base64.push(base64map.charAt(overflow))

		// Add padding
		while (base64.length % 4 != 0) base64.push('=')

		return base64.join('')

	},

	// Convert a base-64 string to a byte array
	base64ToBytes: function (base64) {

		// Use browser-native function if it exists
		if (typeof atob === 'function') return util.stringToBytes(atob(base64))

		// Remove non-base-64 characters
		base64 = base64.replace(/[^A-Z0-9+\/]/ig, '')

		var bytes = []

		for (var i = 0; i < base64.length; i++) {
			switch (i % 4) {
				case 1:
					bytes.push((base64map.indexOf(base64.charAt(i - 1)) << 2) |
					           (base64map.indexOf(base64.charAt(i)) >>> 4))
					break
				case 2:
					bytes.push(((base64map.indexOf(base64.charAt(i - 1)) & 0xF) << 4) |
					           (base64map.indexOf(base64.charAt(i)) >>> 2))
					break
				case 3:
					bytes.push(((base64map.indexOf(base64.charAt(i - 1)) & 0x3) << 6) |
					           (base64map.indexOf(base64.charAt(i))))
					break
			}
		}

		return bytes

	}

}

// Crypto mode namespace
Crypto.mode = {}

})()

module.exports = Crypto